1. Technical Field
The present invention relates in general to radiation inspection systems and methods using the same, and more particularly, to a radiation inspection system and a method using the same allowing visual images to be transmitted sequentially using an electronic shutter.
2. Description of the Related Art
Radiation includes xcex1-rays, xcex2-rays, "sgr"-rays, X-rays, neutron-rays, etc. which cause electrolytic dissociation in reacting with materials. X-rays are electronic waves whose wavelengths are in the range of 10-0.001 nm, having such optical characteristics as reflection and diffraction, etc. The wavelengths can be exactly measured using a diffraction grating.
X-rays have a capability of transmitting or passing through an object. The rate of transmission varies depending upon materials, density and thickness of the object. An X-ray detection method uses this property of X-rays to detect thickness and position of a defective part in the object from the difference in photosensitive intensity of a film photographed by X-rays.
X-rays show the phenomenon of diffraction when transmitted into an object. An X-ray stress measuring method uses this property of X-rays to calculate stress by transmitting X-rays into the object and measuring from diffracted rays a dimensional variation in the distance between faces of a certain crystal lattice to which stress is applied.
A radiation inspection system is a typical non-destructive test (NDT) system which employs and systemizes the X-ray detection method and the X-ray stress measuring method. X-ray transmission characteristics vary depending upon materials, density and thickness of an object to be inspected, so that the X-rays are reflected into X-ray projecting images. The radiation inspection system converts the X-ray projecting images into visual images. The radiation inspection system performs a non-destructive test on a portion of the object which is invisible from the outside, based on the converted visual images.
FIG. 4 is a perspective view schematically showing a conventional radiation inspection system, and FIG. 5 is a perspective view partially showing some elements of the system of FIG. 4 from a different angle. As illustrated, the conventional radiation inspection system is comprised of an X-Y table 57 on which an object 53 to be inspected by NDT rests, an X-ray electronic tube 51 for generating X-rays and projecting the X-rays into the object 53, and an image intensifier 55 for forming visual images from the X-rays having passed through the object 53. The radiation inspection system is further comprised of an image selection unit 60 for selecting desired visual images among visual images formed by the image intensifier 55 and a charge coupled device (CCD) camera 65 for photographing the selected images and outputting them to an image sensor(not shown).
Between the X-ray electronic tube 51 and the image intensifier 55 is disposed the X-Y table 57 on which the object 53 rests and which is movable in X-Y directions. The image intensifier 55 is disposed on a transmission path of he X-rays generated by the X-ray electronic tube 51. On the lower face of the image intensifier 55 is provided a visual image part 56 on which the visual images formed through the image intensifier 55 are projected.
The image selection unit 60 is disposed along the transmission path of the X-rays under the visual image part 56, and comprises a primary galvanometer 61 and a secondary galvanometer 62. The primary galvanometer 61 has a rotary shaft parallel to the plane of the visual image part 56 and the secondary galvanometer 62 has a rotary shaft perpendicular to the plane of the visual image part 56. On the one end of the rotary shaft of the primary galvanometer 61 is mounted a primary reflector 63 for selectively reflecting the visual images from the visual image part 56. On the one end of the rotary shaft of the secondary galvanometer 61 is mounted a secondary reflector 64 for selectively reflecting the visual images reflected by the primary reflector 63, toward the CCD camera 65.
The image selection unit 60 further comprises a galvanometer controller 67 for controlling rotational angles of the primary galvanometer 61 and the secondary galvanometer 62 so as to selectively provide the CCD camera 65 with the visual images projected on the visual image part 56, through a reflection path optically formed by the primary reflector 63 and the secondary reflector 64.
The primary and secondary galvanometers 61 and 62 have very little moment of inertia, to thereby enable a precise servo control at high speed. Accordingly, the primary and secondary galvanometers 61 and 62 are capable of precisely rotating the primary and secondary reflectors 63 and 64 at high speed so as to reflect visual images on any part of the visual image part 56.
The conventional radiation inspection system operates n the following manner. The X-ray electronic tube 51 radiates X-rays toward the area to be inspected on the object 53 while being rotated along a circumferential direction at constant speed. Projected images formed by the X-rays having passed through the object 53 are circumferentially projected on the top face of the image intensifier 55. The projected images on the top face of the image intensifier 55 are converted into visual images through the inside of the image intensifier 55. The visual images are projected on the visual image part 56 positioned on the lower end of the image intensifier 55. The visual images projected on the visual image part 56 are selected by the image selection unit 60 and photographed by the CCD camera 65. The visual images photographed by the CCD camera 65 are synthesized and analyzed by a computer (not shown).
However, the conventional radiation inspection system results in high production cost because of the galvanometers 61 and 62 which are comparatively expensive as an image selection unit 60 for selecting visual images. Additionally, distortion of visual images may be caused by the primary and secondary reflectors 63 and 64 in the course of transferring the visual images to the CCD camera 65, thereby resulting in lowering a reliability of the inspection result.
To solve the above-described problems, a radiation inspection system has been proposed which provides a plurality of image intensifiers and a plurality of CCD cameras corresponding to the number of projected images formed by the X-rays, so that visual images formed through the image intensifier 55 can be directly transmitted into the respective CCD cameras. The radiation inspection system of this type is advantageous in photographing the visual images promptly and precisely, but it still requires a high cost of production.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a radiation inspection system and a method for using the same allowing visual images to be photographed promptly and precisely, but with a lower cost of production.
In accordance with the present invention, the above and other objects can be achieved by the provision of a radiation inspection system comprising a steering radiation electronic tube for projecting radiation onto an object to be inspected, an image intensifier for converting a plurality of projection images formed by the radiation from the steering radiation electronic tube into visual images, the image intensifier having a visual image part on which the visual images are projected, an electronic shutter having a visual image transmission part for transmitting the visual images projected on the visual image part of the image intensifier in sequence, and a camera for photographing the visual images from the visual image transmission part of the electronic shutter in sequence.
Preferably, electric signals are applied synchronously with formation of the visual images to the visual image transmission part causing the sequential transmission of the visual images thereby.
Preferably, the visual image transmission part comprises a plurality of polarizing filters for transmitting or shielding the visual images according to the electric signals received thereby.
It is effective that the polarizing filters are formed of a liquid crystal display (LCD) or a plasma display panel (PDP).
Preferably, the visual images are formed sequentially along a circumferential direction of the visual image part, and the polarizing filters are disposed along a circumferential direction of the visual image transmission part so as to be correspondent with the visual images.
Preferably, the radiation includes X-rays.
According to another aspect of the present invention, the object can be achieved by a radiation inspection method using a radiation inspection system comprising the steps of: projecting radiation from a steering radiation electronic tube onto an object to be inspected, converting with an image intensifier a plurality of projection images formed by the radiation from the steering radiation electronic tube into visual images, the converting step including projecting the visual images onto a visual image part, providing an electronic shutter having a visual image transmission part corresponding to the visual images adjacent the visual image part, transmitting the visual images of the visual image part sequentially through the visual image transmission part, and photographing the visual images passing through the electronic shutter in sequence.
Preferably, the transmitting step includes applying electric signals synchronously with formation of the visual images to the visual image transmission part.
Preferably, the visual image transmission part comprises a plurality of polarizing filters for transmitting or shielding the visual images, and the transmitting step includes applying of the electric signals to the polarizing filters.
It is effective that the polarizing filters are formed of a liquid crystal display (LCD) or a plasma display panel (PDP).
Preferably, the converting step includes sequentially forming visual images along a circumferential direction of the visual image part, and the polarizing filters are disposed along a circumferential direction of the visual image transmission part so as to be correspondent with the visual images.
Preferably, the radiation projected from the steering radiation electronic tube includes X-rays.